/*
* This file is part of the Jikes RVM project (http://jikesrvm.org).
*
* This file is licensed to You under the Common Public License (CPL);
* You may not use this file except in compliance with the License. You
* may obtain a copy of the License at
*
* http://www.opensource.org/licenses/cpl1.0.php
*
* See the COPYRIGHT.txt file distributed with this work for information
* regarding copyright ownership.
*/
package org.mmtk.plan.refcount.generational;
import org.mmtk.plan.refcount.RCBaseMutator;
import org.mmtk.plan.refcount.RCHeader;
import org.mmtk.policy.CopyLocal;
import org.mmtk.policy.Space;
import org.mmtk.utility.Constants;
import org.mmtk.utility.alloc.Allocator;
import org.mmtk.vm.VM;
import org.vmmagic.pragma.*;
import org.vmmagic.unboxed.*;
/**
* This class implements <i>per-mutator thread</i> behavior and
* state for the <i>GenRC</i> plan, a generational reference
* counting collector.<p>
*
* Specifically, this class defines mutation-time allocation (allocation
* into the nursery and "pre-tenuring" into the mature space), write barriers
* and per-mutator collection semantics (such as flushing rememberd sets
* flushing and initializing allocators).<p>
*
* @see GenRC for a description of the generational reference counting
* algorithm.<p>
*
* FIXME Currently GenRC does not properly separate mutator and collector
* behaviors, so most of the collection logic in GenRCMutator should really
* be per-collector thread, not per-mutator thread.
*
* @see org.mmtk.plan.refcount.RCBaseMutator
* @see GenRC
* @see GenRCCollector
* @see org.mmtk.plan.StopTheWorldMutator
* @see org.mmtk.plan.MutatorContext
*/
@Uninterruptible public abstract class GenRCMutator extends RCBaseMutator implements Constants {
/****************************************************************************
* Instance fields
*/
public CopyLocal nursery = new CopyLocal(GenRC.nurserySpace);
/****************************************************************************
*
* Mutator-time allocation
*/
/**
* Allocate space (for an object)
*
* @param bytes The size of the space to be allocated (in bytes)
* @param align The requested alignment
* @param offset The alignment offset
* @param allocator The allocator number to be used for this allocation
* @param site Allocation site.
* @return The address of the first byte of the allocated region
*/
@Inline
public final Address alloc(int bytes, int align, int offset, int allocator, int site) {
if (allocator == GenRC.ALLOC_NURSERY) {
return nursery.alloc(bytes, align, offset);
}
return super.alloc(bytes,align,offset,allocator, site);
}
/**
* Perform post-allocation actions. For many allocators none are
* required.
*
* @param ref The newly allocated object
* @param typeRef the type reference for the instance being created
* @param bytes The size of the space to be allocated (in bytes)
* @param allocator The allocator number to be used for this allocation
*/
@Inline
public final void postAlloc(ObjectReference ref, ObjectReference typeRef,
int bytes, int allocator) {
if (allocator != GenRC.ALLOC_NURSERY) {
super.postAlloc(ref,typeRef,bytes,allocator);
}
}
/**
* Return the space into which an allocator is allocating. This
* particular method will match against those spaces defined at this
* level of the class hierarchy. Subclasses must deal with spaces
* they define and refer to superclasses appropriately. This exists
* to support {@link org.mmtk.plan.MutatorContext#getOwnAllocator(Allocator)}.
*
* @see org.mmtk.plan.MutatorContext#getOwnAllocator(Allocator)
* @param a An allocator
* @return The space into which <code>a</code> is allocating, or
* <code>null</code> if there is no space associated with
* <code>a</code>.
*/
public final Space getSpaceFromAllocator(Allocator a) {
if (a == nursery) return GenRC.nurserySpace;
return super.getSpaceFromAllocator(a);
}
/**
* Return the allocator instance associated with a space
* <code>space</code>, for this plan instance. This exists
* to support {@link org.mmtk.plan.MutatorContext#getOwnAllocator(Allocator)}.
*
* @see org.mmtk.plan.MutatorContext#getOwnAllocator(Allocator)
* @param space The space for which the allocator instance is desired.
* @return The allocator instance associated with this plan instance
* which is allocating into <code>space</code>, or <code>null</code>
* if no appropriate allocator can be established.
*/
public final Allocator getAllocatorFromSpace(Space space) {
if (space == GenRC.nurserySpace) return nursery;
return super.getAllocatorFromSpace(space);
}
/****************************************************************************
*
* Collection
*/
/**
* Perform a per-mutator collection phase.
*
* @param phaseId The collection phase to perform
* @param primary Perform any single-threaded activities using this thread.
*/
@Inline
public void collectionPhase(short phaseId, boolean primary) {
if (phaseId == GenRC.PREPARE) {
nursery.rebind(GenRC.nurserySpace);
}
super.collectionPhase(phaseId, primary);
}
/****************************************************************************
*
* Write barriers.
*/
/**
* A new reference is about to be created. Perform appropriate
* write barrier action.<p>
*
* In this case, we remember the address of the source of the
* pointer if the new reference points into the nursery from
* non-nursery space.
*
* @param src The object into which the new reference will be stored
* @param slot The address into which the new reference will be
* stored.
* @param tgt The target of the new reference
* @param metaDataA An int that assists the host VM in creating a store
* @param metaDataB An int that assists the host VM in creating a store
* @param mode The mode of the store (eg putfield, putstatic etc)
*/
@Inline
public final void writeBarrier(ObjectReference src, Address slot,
ObjectReference tgt, Offset metaDataA,
int metaDataB, int mode) {
if (GenRC.GATHER_WRITE_BARRIER_STATS) GenRC.wbFast.inc();
if (RCHeader.logRequired(src))
writeBarrierSlow(src);
VM.barriers.performWriteInBarrier(src, slot, tgt, metaDataA, metaDataB, mode);
}
/**
* Attempt to atomically exchange the value in the given slot
* with the passed replacement value. If a new reference is
* created, we must then take appropriate write barrier actions.<p>
*
* @param src The object into which the new reference will be stored
* @param slot The address into which the new reference will be
* stored.
* @param old The old reference to be swapped out
* @param tgt The target of the new reference
* @param metaDataA An int that assists the host VM in creating a store
* @param metaDataB An int that assists the host VM in creating a store
* @param mode The context in which the store occured
* @return True if the swap was successful.
*/
public boolean tryCompareAndSwapWriteBarrier(ObjectReference src, Address slot,
ObjectReference old, ObjectReference tgt, Offset metaDataA,
int metaDataB, int mode) {
if (RCHeader.logRequired(src))
writeBarrierSlow(src);
return VM.barriers.tryCompareAndSwapWriteInBarrier(src, slot, old, tgt, metaDataA, metaDataB, mode);
}
/**
* A number of references are about to be copied from object
* <code>src</code> to object <code>dst</code> (as in an array
* copy). Thus, <code>dst</code> is the mutated object. Take
* appropriate write barrier actions.<p>
*
* In this case, we simply remember the mutated source object.
*
* @param src The source of the values to copied
* @param srcOffset The offset of the first source address, in
* bytes, relative to <code>src</code> (in principle, this could be
* negative).
* @param dst The mutated object, i.e. the destination of the copy.
* @param dstOffset The offset of the first destination address, in
* bytes relative to <code>tgt</code> (in principle, this could be
* negative).
* @param bytes The size of the region being copied, in bytes.
* @return True if the update was performed by the barrier, false if
* left to the caller (always false in this case).
*/
@Inline
public final boolean writeBarrier(ObjectReference src, Offset srcOffset,
ObjectReference dst, Offset dstOffset,
int bytes) {
if (GenRC.GATHER_WRITE_BARRIER_STATS) GenRC.wbFast.inc();
if (RCHeader.logRequired(dst))
writeBarrierSlow(dst);
return false;
}
/**
* This object <i>may</i> need to be logged because we <i>may</i>
* have been the first to update it. We can't be sure because of
* the (delibrate) lack of synchronization in the
* <code>logRequired()</code> method, which can generate a race
* condition. So, we now use an atomic operation to arbitrate the
* race. If we successful, we will log the object, enumerating its
* pointers with the decrement enumerator and marking it as logged.
*
* @param src The object being mutated.
*/
@NoInline
private void writeBarrierSlow(ObjectReference src) {
if (VM.VERIFY_ASSERTIONS) {
VM.assertions._assert(!Space.isInSpace(GenRC.NS, src));
}
if (RCHeader.attemptToLog(src)) {
if (GenRC.GATHER_WRITE_BARRIER_STATS) GenRC.wbSlow.inc();
modBuffer.push(src);
decBuffer.processChildren(src);
RCHeader.makeLogged(src);
}
}
}